The present invention relates generally to electrical load controls, such as standard switches, as well as to fault protection devices, such as ground fault circuit interrupting (GFCI) devices, and arc fault circuit interrupting (AFCI) devices.
The electrical wiring device industry continues to witness an increasing call for fault-interrupting devices designed to interrupt power to various loads, such as household appliances, consumer electrical products and branch circuits. For example, electrical codes currently require electrical circuits in home bathrooms and kitchens, as well as exterior circuits, to be equipped with ground fault circuit interrupters. These electrical codes are often met using GFCI receptacle-type devices, such as those described in commonly owned U.S. Pat. Nos. 6,040,967 and 7,463,124, the entirety of each of which is hereby incorporated herein by reference.
GFCI or AFCI receptacle-type devices are used to protect against electrical shock due to ground fault conditions or arcing conditions, respectively. A GFCI device is basically a differential current detector operative to trip a contact mechanism when a certain amount of unbalanced current is detected between the phase wire and neutral wire of an alternating current (AC) electrical power line. A typical GFCI device includes electrical components such as transformers, a relay and circuitry for detecting a ground fault condition. A typical AFCI device includes a protection component that is used to detect arcs and whose output is used to trigger a circuit-interrupting mechanism in a similar manner to a GFCI device.
More particularly, available GFCI devices, such as the devices described in the above-incorporated patents, as well as in commonly owned, U.S. Pat. No. 4,595,894 (the entirety of which is hereby incorporated herein by reference), use an electrically-activated trip mechanism to mechanically break an electrical connection between the line side and the load side of the wiring device. Such devices are resettable after they are tripped by, for example, the detection of a ground fault. In the device discussed in U.S. Pat. No. 4,595,894, the trip mechanism used to cause the mechanical breaking of the circuit (i.e., the conductive path between the line and load sides) includes a solenoid or trip coil. A TEST button is used to test the trip mechanism, as well as the circuitry used to sense faults, and a RESET button is used to reset the electrical connection between the line and load sides.
AFCI devices, such as the devices described in commonly owned, U.S. Pat. Nos. 7,003,435 and 7,535,234 (the entirety of each of which is hereby incorporated herein by reference), may be stand-alone devices, or used in combination with other circuit interrupting devices, such as GFCI devices. AFCI devices protect against potentially dangerous arc fault conditions. An AFCI fault detector monitors for the presence of arcing, and upon detection of arcing, generates an output signal to activate a circuit-interrupting mechanism to switch open, for example, a phase line and a neutral line coupled to the circuit-interrupting mechanism of the AFCI device.